1. Field of the Invention
The present invention relates to an image reading apparatus used for a facsimile apparatus, a scanner, or the like.
2. Related Background Art
As an image reading apparatus for reading an original image, there is an apparatus having three photoelectronic conversion device arrays formed on a sensor substrate, and color filters arranged above the photoelectric conversion device arrays to split light into three color components, i.e., red (R), green (G), and blue (B) light components. In such an image reading apparatus, three light components, i.e., R, G, and B light components of light reflected by an original are simultaneously received through a lens to accumulate charges on the sensors, and R, G, and B image signals are output.
However, since the photosensitivity of a sensor with a filter becomes lower as the wavelength is shorter, the output level of the B photoelectric conversion device array is much lower than that of the R or G photoelectric conversion device array, resulting in a degradation in S/N ratio. For this reason, a blue image cannot be properly read. For example, when a solid blue original is to be read and output from an output device such as a color BJ printer, the color balance of the image undesirably becomes nonuniform.